Lightning started four large wildfires in central Idaho in early August 2013. After igniting on August 8, the Elk Complex fire and Pony Complex fire both grew rapidly on August 10, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired this image. The red outlines show the fire area as detected by MODIS.

The Elk Complex Fire appears to have generated a large pyrocumulus cloud, which is formed by fire-heated air that rises rapidly into the atmosphere. The photo, originally published on the Elk Complex Incident site, shows the white cloud rising above the gray smoke plume on the afternoon of August 10. The Elk Complex Fire threatened hundreds of homes and forced evacuations in the Pine-Featherville region and in the small community of Prairie. It is the highest priority fire in the nation. By August 12, the fire had burned 90,249 acres of grass, brush, and conifer stands, making it the second-largest active fire in the United States.

The nation’s largest wildfire is the Pony Complex Fire, which forced evacuations in Mayfield and Canyon Creek. Burning through grass, sagebrush, and timber, this fire was 119,543 acres in size by August 12. It was 20 percent contained and had a high potential for growth.

The McCan and Beaver Creek fires were initially grouped together as the Beaver Creek Complex, but firefighters quickly divided the two to simplify management. Both fires are burning in difficult terrain. The McCan fire has burned 23,860 acres since August 7. The Beaver Creek fire started on August 9 and has burned 24,120 acres.

Together the four fires have burned more than 400 square miles (257,772 acres). 1,724 firefighters are working to control or manage the fires. The smoke is having a toll on public health. The Idaho Department of Health and Welfare’s warned residents of central Idaho—including the populated areas around Boise and Twin Falls—that air quality had reached unhealthy levels.